Flexible grooved pipe

ABSTRACT

A helically-corrugated flexible pipe wound from metal foil or sheet metal strips is characterized in that the grooves or ribs are upset or pressed in a gradually increasing manner toward the ends of the pipe.

United States Patent 1191 1 3,738,394 Westerbarkey June 12, 1973FLEXIBLE GROOVED PIPE 2,954,802 10/1960 Duff 138/122 [75] Inventor:Leonard Westerbarkey, Gutersloh,

Germany Primary Examiner-Martin P. Schwadron [73] Ass1gnee: FirmaWestflexwerk L. & F., Asst-slam Examiner A zupcic Westerbarkey,Gutersloh, Germany Atwmey Richards & Geier [22] Filed: Jan. 29, 1971[21] Appl. No.: 111,008

[57] ABSTRACT [52] US. Cl 138/122, 138/173, 138/129 [51] Int. Cl. F1619/18, F1619/00 5s 1 Field of Search 138/109, 122, 129, Ahellcally-corrugated flexlble p p wound from metal [38/134, 178, 7 foilor sheet metal strips is characterized in that the grooves or ribs areupset or pressed in a gradually in- [56] References Cited creasingmanner toward the ends of the pipe.

UNITED STATES PATENTS 2,986,169 5/1961 McCormick 138/109 4 Claims, 3Drawing Figures FLEXIBLE GROOVED PIPE This invention relates to aspirally grooved flexible pipe wound from metal foil or sheet metal. Theinvention refers more particularly to a pipe of this type which is builtas a pipe section into a waste gas conduit or the like to absorbvibrations and balance elongations.

Pipes of this type are preferably made of metal foil, for example,refined steel, and they are subjected to very strong stresses, primarilyvibration strains but also other mechanicaland thermic as well aschemical stresses. Experiments which were actually carried out haveshown that although such pipes are very well suited to be inserted, forexample, as intermediate pieces to absorb vibrations in exhaust gasinstallations of motor cars, it was always discovered that cracks andalso breakages take place in the flexible pipe at or close to itsconnection with the rigid pipes.

The present invention is based on the discovery that this phenomenon iscaused by the fact that apparently the connecting parts or thetransition parts are subjected to excessive strains since the vibrationsstart there and the material is thereby overstrained.

Therefore, an object of the present invention is to produce a pipe whichwill absorb vibrations and balance extensions, which is subjected tostrains which are as uniform as possible along its entire length andwhich in its structure gradually changes from a rigid pipe into aflexible pipe.

Other objects of the present invention will become apparent in thecourse of the following specification.

In the accomplishment of the objectives of the present invention it wasfound desirable to provide a helically corrugated flexible pipe woundfrom metal foil or sheet metal and to upset or press its corrugations ina gradually increasing manner toward the ends of the pipe. The length inwhich the ribs are pressed in a gradually increasing manner toward theends of the pipe corresponds to that of at least one diameter of thepipe but is preferably two or more pipe diameters. The compression ofthe corrugations increasing gradually to the end of pipe does not haveto cover the entire circumference but can be arranged in individualwedge-shaped areas of the pipe wall widening toward the end of the pipe.'The ends of the pipe have a flexibility which is gradually reduced torigidity.

The invention will appear more clearly from the following detaileddescription. when taken in connection with the accompanying drawingshowing by way of example only, preferred embodiments of the inventiveidea.

In the drawing:

FIG. 1 is a perspective view of a flexible pipe.

FIG. 2 is a diagram illustrating in cross-section the shape of a wall ofthe pipe shown in FIG. 1 at the end of the pipe.

FIG. 3 is a front view of a differently shaped pipe.

The pipe shown in FIGS. 1 and 2 is wound from sheet metal strips and isprovided with circumferential helically extending corrugations withpeaks ll separated by troughs 12. The flanks of the peaks havecomparatively short portions 13 which are straight and which preferablyextend parallel to each other.

The pipe 10 is wound from ribbed strips of refined steel. The strips canconsist of one or several layers and their edges are joined by folds.The ends of the pipe 10 may be introduced into and fixed to funnel-likeconnections l4 and 15 of a rigid pipe of an exhaust gas device of motorcars, stationary combustion motors or the like.

As shown in FIG. 2, at the ends of the pipe the corrugations aregradually more and more compressed until they assume a shape wherein theinitially round peaks 11 and the initially round troughs l2 become moreand more flat (18 in FIG. 2) and the spaces between these round portionsbecome gradually less and less until shortly before the end of the pipethe flattened'ribs touch each other.

This or change of shape of the corrugations results in that the pipegradually loses its flexibility toward its end while its rigidityincreases correspondingly. Vibrations or other mechanical stressesintroduced into the pipe 10 by the rigid pipe 14, 15 are completelyabsorbed due to this specific shape of the ends of the pipe 10. Theserigid ends of the pipe 10 will vibrate in the same manner as theconnected rigid pipe 14, 15. Since the pipe 10 becomes gradually moreflexible and bendable at a distance from the pipe ends 14 and 15, theintroduced vibrations will be more uniformly distributed and can bebetter received and absorbed. Extensive lengthy experimentation hasshown that the stability of a pipe made in accordance with the presentinvention is greater by at least the tenth power than those of othersimilar pipes the ends of which have not been shaped. It appears that inthe case of such unshaped pipes the entire vibration energy is receivedat their ends, so that the material is excessively stressed there.

By way of example, the change in shape or the compression of the ends ofthe pipe 10 can be carried out by placing the pipe tightly upon amassive bar and then applying to the ribs a pressure tool or a rollingtool with a pressure which increases toward the ends of the pipe untilthe profile shown in FIG. 2 is produced.

However, it is not absolutely necessary to change the shape of thecorrugations upon the entire circumference of the pipe. FIG. 3 shows apipe 16 wherein the ribs are changed in a wedge-shaped section 17 whichwidens toward the end of the pipe. Obviously there may be several suchsections.

I claim:

1. A helically corrugated flexible wound metal pipe, the corrugations ofsaid pipe being increasingly radially compressed towards at least oneend of the pipe.

2. A pipe in accordance with claim 1, wherein the corrugations an andend of the pipe are increasingly compressed over a length of the pipecorresponding to at least one diameter of the pipe. 1

3. A pipe in accordance with claim 1, wherein the corrugations areincreasingly compressed in at least one wedge-shaped area of the pipewall, said area widening towards the end of the pipe.

4. A pipe in accordance with claim 1, wherein the flexibility of thepipe gradually diminishes toward the ends of the pipe, said ends beingrigid.

1. A helically corrugated flexible wound metal pipe, the corrugations ofsaid pipe being increasingly radially compressed towards at least oneend of the pipe.
 2. A pipe in accordance with claim 1, wherein thecorrugations an and end of the pipe are increasingly compressed over alength of the pipe corresponding to at least one diameter of the pipe.3. A pipe in accordance with claim 1, wherein the corrugations areincreasingly compressed in at least one wedge-shaped area of the pipewall, said area widening towards the end of the pipe.
 4. A pipe inaccordance with claim 1, wherein the flexibility of the pipe graduallydiminishes toward the ends of the pipe, said ends being rigid.